The diagram shows the forces involved in lifting a heavy object of mass L with the arms. If the weight of the object is L=300N and assuming the centre of gravity of the trunk is 2/3 of the way up the spine between the lumbosacral joint and the arms, determine:

a) The compressive force, Sc, on the lumbosacral disc.

b) The angle, θ, that the force, S, acts to the column.

c) If the force required to rupture the disc is 15,000N determine the maximum mass (in kg) that can be lifted by the arms without causing damage to the disc. (Assume that the total body weight is 700N and that 60% of the total body weight is supported by the spine in this configuration).

Assume g=10 ms^-2 where necessary